TH QFG build

News & Discussion
Post Reply
User avatar
Pav
Wiggling with Experience
Posts: 392
Joined: Sat Mar 19, 2016 3:21 pm
Location: UK Hampshire

TH QFG build

Post by Pav »

IMG_20230116_171847480.jpg
I was waiting for a 4001BE when this image taken.
Now complete as shown in 2023 show us yr builds:
viewtopic.php?p=3894237#p3894237

Some build observations should someone plan to build:
* its a compact build so smaller 0.4w resistors helped.

* the badly fitting 4.7n wima 3% timing cap was a swap in for a 10% Kemet I had soldered in - presuming
3% improves timing..but it was a real pain to remove the kemet in the cramped space, and have clear holes.

* calibration guidance is on the https://www.birthofasynth.com/Thomas_He ... s/QFG.html
- it suggested i swap out the wima for 1 uf for v/octave calibration..but given the pain to get the wima in
i didnt take this advice. Trying out different values you might want to start with a temporary socket (eg SIL)

* on first power on, the 270deg led failed to the light, while 90 deg was seeing double hits.
Continuity tests showed leds working, but then the scope revealed the 270deg output signal was never going positive.
Calibrating with the trimmer solves this led issue and i achieved the triangle centered around zero volts and saw just
under +/- 4v peak to peak.

* Im willing to be told i am wrong but the labeling of the 20way connector diagram on Foniks site for the 270deg LED lit up the 90deg
and vice versa. I was using an old battery and a resistor to test the leds thru the 20way, so might just be a slapdash continuity test.
Just thought i mention.

Now have a working module, and happy bunny.
Thanks Fonik.
rgds Pav
Post Reply

Return to “fonitronik”